Size controlling mechanism for boring machines and the like



Bea-231941. I BLOOD 2,267,186

SIZE CONTROLLING MECHANISM FOR BORING MACHINES AND THE LIKE Original Filed Aug. 5, 1938 lnventor Ha'rold L. Blood attor Patented Dec. 23, 1941 SIZE CONTROLLING MECHANISM FOR BORING MACHINES AND THE LIKE Harold L. Blood, Worcester, Mass, The Heald Machine Company,

of Massachusetts Mass, a corporation assignor to Worcester,

Contlnuation oi' application Serial No. 222,858, I

s application June 1, 1939,

August 3, 1938. Thi Serial No. 276,845

1'7 Claims.

The present invention relates to machines which are used to impart a predetermined finished dimension to corresponding surfaces of a succession of similar workpieces, and the invention is particularly applicable to boring machines where it is customary for the cutting tool to operate on a relatively large number of successive workpieces before there is need to make any adjustment of the tool to compensate for the wearing-away of its cutting surface. This 'application is a continuation of my Serial No. 222,858, filed August 3, 1938, for Size-controlling mechanism for boring machines and the like.

In machines of this character the initially established position of the cutting tool relative to the axis of the workholder for the production positively from the of a succession of workpiece bores of a prede termined finished size can generalhr be maintained without adjustment during the machining of quite a number of successive workpieces by reason of the fact that the tool is of extremely hard material and can operate for a considerable time before perceptible wear occurs. After repeated machining operations are performed by the tool, however, the latter does wear down to such an extent that it is no longer capable without readjustment of imparting the desired flnished dimension to the subsequently presented workpieces, since such dimension is dependent upon the distance of the cutting surface of the tool from the axis of rotation of the tool or of the workpiece, as the case may be. Adjustment of the tool is then essential if the successive workpieces are all to be finished to the same established dimension.

In the Blood Reissue Patent No. 20,634 of January 25, 1938, as well as in my copending companion application Serial No. 220,566, filed July 21, 1938, is disclosed a boring machine organization wherein at the completion of each boring opera ion, a gage or calipering mechanism is automatically brought into action to test the finished dimension of the workpiece then in the machine. said mechanism being wholly without influence on the tool in all cases where the desired finished size of the so-tested workpieces has been attained, but said mechanism functioning to produce a wear-compensatory adjustment of said tool if and when the so-tested workpiece has not been finished to the desired size.

My present invention provides a similarlyiuncioning organization adapted to give, when needed. a wear-compensatory adjustment or repositioning of the tool, and it utilizes in large measure the same instrumentalities for causing (CL'li- -3) K, the tool, at the completion of the boring stroke ting action of the rotating tool 3.

workpiece, to be backed .ofl finished workpiece surface, so the latter wlllnot be marred or'scratched by the tool on the reverse or withdrawal stroke.

Other and further objects and or traverse of each tailed, description taken ,in connection accompanying drawing, in which- Fig. 1 is a front elevation of a machine em bodying the invention, certain of the parts bein in section to show the construction.

through.

chine oi well known type, as for example, a ma-.' to that of the Bloodrechine somewhat similar issue patent above referred to. In theillustrated machine a base I supports a horizontally movable table 2 slidable on ways, actuated in any suitable way, as by fluid under pressure .to produce a relative traverslngmovement between a rotary cutting tool 3 and a workpiece a for a longitudinal movement through the workpiece bore of therotary tool. Toobtain this relative movement, either the tool or the workpiece may be carried by the table; as here shown, by way of example, the movable table carries a suitable workholder 4 in which the workpiece a is secured, as by a suitable clamp 5. The tool 3 is rotatively supported in a tool head 6 mounted on a bridge I which spans the guideways provided by the machine base. The boring operation occurs when the table 2 moves to. the left from the position shown in Fig. 1, to subject the workpiece-bore, for its entire length, to the cutreverses,'moving back to the position shown in Fig. 1, to permit replacement oi the finished next workpiece to be operated workpiece bythe v upon. The reversal of the table 2 is effected when a dog 8 on said table engages a reversing lever 9 which is operatively connected to a reversing valve l0 (Fig. pressure system by which said table I is actuated;

such engagement shifts the reversing valve into Fig. 4," and causes movethe. position shown by advantagesof I the invention will appear from the following dewith the along the line showing of certain of the not shown, and

The table then 4) provided in the fluid" ment of the table to the right to carry the workpiece to the inoperative position shown by Fig. 1. As the returning table reaches the position of Fig. .1 it is brought to rest by any suitable means, not shown.

Referring now to Fig. 41, the fluid pressure mechanism by which the table is actuated comprises a cylinder H, mounted within, and held in flxed relation to, the base of the machine. A projecting rod l2 secured to a piston, not shown within said cylinder, is suitably connected to the table 2. Fluid under pressure from a pump it is directed through a conduit I 4 to an inlet port II in the casing 16 of reversing valve ll. Ports 11 and II in the casing are connected to the opposite ends of the cylinder Ill by pipes i and I! and the casing I4 is also provided with an outlet port 20. In response to movements of the valve II by the reversing lever I. fluid under pressure is directed alternately to opposite ends of the cylinder II to provide for the longitudinal traversing movements of the table.

Referring now to Fig. 1, each successive workpiece a is supported with its axis substantially horizontal'in the workholder 4, and a housing 2! is mounted on the table in line with the workholder 4 to support a gage 22 in accurate alinement with the bore of the workpiece. The gage is carried by a gage rod 28 extending from a plunger 24 slidable in a horizontal bore 2! in the housing 2 i. The gage member 22 corresponds in size or diameter to the desired flnished dimension of the workpiece bore, and is arranged to be brought into operative relation to each workpiece in the machine, immediately following the action of the rotary boring tool 4 thereon.

with reference again to Fig. 4, the plunger which carries the gage rod is moved toward and away from the workpiece by fluid under pressure. A conduit 24 provides a connection between the pipe I! and a port 28' at the inner or left hand end of the bore 2! (the upper end Fig. 4) and a pipe 21 provides a connection between the pipe ii' and a port 21' at the outer or right hand endof the bore 25 (the lower end,

Pig. 4). Thus, as, the table moves to the left to bring the tool and workpiece into operative relation, left hand end of the bore 25 to hold the gage away from the workpiece and,as the reversing valve is shifted at the left hand end of the table fluid under pressure is directed, to the movement, fluid under pressure is directed to the right hand end of the bore 2i to cause a movement of the gage to the left for entry within the workpiece bore if the latter is finished to the desired size.

The gage-moving'plunger '24 acts also as a valve, and to this end has a centrally located groove 24 which in the above-described extreme positions of said plunger is out of line with opposed ports 29 and 3| opening from the bore 2! of housing 2|. The groove 24 comes into line with theports 29 and II only when the gage 22.

on its leftward movement, is unable to enter the workpiece bore-as will hereinafter appear. The port 30 is connected by a conduit 14 to a port 36 in a casing 36 (Fig. 4) which contains a vertically siidable piston valve 21, consisting of two piston portions separated by a reduced portion 46. The casing 36 has a port 38 connected by a conduit 29 to the conduit l4 between the pump l2 and the reversing valve casing It.

The valve 31 has an upwardly projecting stem 44, which, as best shown in Fig. 1, is in a posi- 4i carried by a block 42 laterally adjustable on the front of the table. The dog 4| is pivoted on a pin 43 and is free to rock counterclockwise to allow the dog to pass without effect over the upper end of the stem during each movement of the table to the left. Upon each reverse movement of the table to the right, however, the swinging movement of the dog 4| is limited by a shoulder 44 on the block and thusthe dog forces the valve I1 downwardly to establish momentarily a fluid connection around the reduced portion '45 of the valve from port 38 to port 35, thereby connecting the conduits 34 and 3!. The valve 21 is normally held in the upper position shown by a coil spring 46.

If the gage 22, on its above-described movement to the left as the tool I withdraws from a workpiece bore, is unable to enter said bore, that is, if its full movement to the left is prevented by engagement between the gage and the end of the workpiece by reason of the workpiece bore being too small, then the reduced'portion of the plunger 24 establishes a fluid connection from port 30 to port 29. Then when the valve 31 is subsequently shifted downwardly by the dog 4|, during movement of the table to the right, the way is open for fluid under pressure to pass from pump it clear through to the port 24, hereinafter described, of

On the other hand, whenever saidgage 22- can make its full left hand movement into the bore of any workpiece that has been operated upon by the tool I, then the ports 28 and 30 are closed on from each other by the plunger 24, in consequence of which no such tool compensating movement can take place.

Referring now to Fig.1. the toolhead I, which is mounted on the bridge 1, has iournalled therein a rotatable hollow spindle 41. the left hand end of which carries apulley turning movement of the cap within the ring 51 and relative to the flange to vary, as'hereinafter described, the projechaving a pair of angular oppositely-facing cutouts or recesses 32 and 33, the latter receiving respectively the pawls 64 and 64, which are pivotally mounted in arcuate notches 82 and 42 of said plate. Said pawls 44 and 65 are normally forced outwardly by springs 68 and 61 respectively, into engagement with the teeth 68 of cap 52, and by reason of their opposed they preventany relative rotative movement, in either direction, between the plate 8| and the cap 58, near :the pawl 85, is a pin 68,-which, with the occurrence of sufflcient counterclockwise turning of plate ii and cap 52 relative to spindle 52, ,Projecting from the end face of flange arrangement,

41, serves to disengage'the-pawl 85 from the said plate, fortransmission by the latter, through: pawls 64 and 85 to the cap 52 which carries the' boring. tool 3. Engaging pin 14 on the opposite side from the shoulder 14' is an arcuate plunger the latter is slidable in an arcuate recess 18 in the pawl plate and is urged against the pin 14 by a coil spring 11 in the bottom of said recess. With this arrangement, and regardless of whether the parts-.58, 6| and 52 be stationary, or be rotating'counterclockwise in unison,-it is evident that am outward radial movement of pin 1| will produce. in response to the camming actionbetween surfaces 12 and 13 the counterclockwise advance of the plateBl (and with it the -.cap 52) relative to the flange 58 and spindle l1. v :1

For moving the plunger 1i radially outward the hollow spindle has a rod 18 extending axially therethrough and having an oblique or bevelled inner ,end 19 for engagement with a similarly bevelled end surface 80 on a wedge 8| which is radially slidable in a groove 82 of the stud 58 forming part of .the cap 52. The outer surface of the wedge 8| engages with the inner end of the pin-1| and accordingly any movement of the rod to the right, Figs. land 2, will produce a radially outward-movement of the pin 1|.

'The outer or left hand end of the rod 18 min a position tobe engaged by the head of a bolt 83 which:is adjustably mounted in the end of a plunger 84, thelatter being slidable in a bore 88 ;of a vcylinder 85 secured to the bridge 1. The plunger 84 is in line with and is engaged by a second plunger slightly larger indiameter than the plunger and slidable in a bore 81 of the cylinder 85, the bore 81 being larger in diameter than the bore 88 in which the plunger 881s slidable.

The plungers 84 and 88 are arranged to be moved to the right, Fig. 1, upon access of pres sure fluid to their respective bores 88 and 81. To

this end, as shown in Fig. 4, a conduit 80 extendshereinafter described,-a temporary back-odor inward displacement of the tool-this prevent ng the newly-finished bore from being scratched or marred by the tool on-saidxreturn or reverse stroke of thetable. Also, 'atjlessfrequentand.irregular intervals, said rod .18 may be-given a more extended right hand movement, brought about by admission of the pressure fluid behind the plungerj8l.on those occasionswhen the gage 22 is unable to enter a finished workpieceborethis producing as hereinafter described anout ward repositioning of the tool which compensates for the wear that has resulted in an oifsizeworkpiece. The operation of the mechanism is as follows:

With a workpiecela sultablyheld in thegwork holder 4 by clamp 5, a movement of the table-2.; to the left, for a boringoperation on said work. piece is initiated by manual shifting of the re-,

versing lever 8, eitherdirectly or-through the medium of a control lever 83 on the front ofv the machine, thereby shifting the reversing valve :lili to establish a fluid connection from the pump I3 to the right hand end .of the table cylinder: H, and also, through conduit 28 against'the left. hand'end of gage-moving plunger-14, to hold the gage 22 away from the end of the workpiece.

The table 2 consequently moves to-the left, Fig. 1,

carrying the workpiece a'past the rotating .tool" 8 for a cutting operation on the workpiece'borer As soon as this movement hasibrought the right hand end-of the workpiecea beyond the tool 8, the table 2 is reversed automatically by engagement of dog 8 with lever 9, to rock valve l8 into its other position, thereby initiating a return or right hand movement of tablei; this reverse movement of the table carrying the workpiece a to the right, effects the withdrawal through thefln shed bore of saidworkpiece of the tool 8.:

As an incident to each suchreversenorwithdrawal movemenhfluid under pressure is'directed through conduits 21 and, against the'outer end.

of plunger 86, causing a'shortmovement of the latter, which through plunger 88 is communicated I to the rod 18 to produce a slight counterclockwise from pipe 21 to a port 89 of bore 81, behind the plunger88, and a conduit 92 extends from port 28 to a port 9! behind the plunger 84; said port 9!" remains open; despite movement of plunger 88'to the right, 'by reason of the fact that said plunger has a reduced portion 88' abutting the plunger- 84, said reduced portion being only slightly larger than the bore '88. Periodically,'at eachreversal movement of the plate. 6| suflicient to obtain an inward radialback-ofl of tool 8 from its normal operating position, so that said tool on said re verse or withdrawal movement of the workpiece,- will be prevented from scratching or marring the flnished surface of the workpiece bore." To this end, the aforesaid short right handmovem'ent of rod 18 is utilized to impart,- by the surfaces 18 and 88, a short outward'movementto the pin-1| by reason of the latter'sbevelled engagement at this outward movement 12, 18 with the pin14, causes a temporary small counterclockwise motion of the plate GI and cap52'relative to-the flange 58, and accordingly, by reason of the e'c-- centricity of stud 53, the result of this angular motion i' a. slight radial retraction vof the tool 3 fromit normal operatingposltion. Onxsuchl counterclockwise motion of the plate 8| the' compression; l and thus the: is available-to restore the spring ll-undergoes force of said spring tool to its normal operatingepositionaafter the tables reverse or'withdrawal movement hasbeen completed and after the" pressureeof the fluid" against theplunger 86 has been relieved, asthe result of rocking the valve It! to its other position, preparatory to a boring operationon. the new workpiece a inserted in themachine.

That is to say, following each'sboring stroke, there occurs a back-off of the tool 3, so 'that on the ensuing return or' withdrawal stroke, the

workpiece bore will not be contacted by said tool. This back-oil which is eil'ective on the tool until the boring operation on the next workpiece a is started, involves the joint counterclockwise angular movement of plate 6| and cap 52 which is produced by a short endwise displacement of rod ll under the influence of plunger 86. Such short displacement procures through pin H, a slight counterclockwise turning of plate ll, less than enough to engage pawl 65 with pin 68, and which is communicated by pawl 65 to the cap 52; consequently, the back-oil occurs because of the eccentricity ot the stud 53 to the stub shaft 54. At the same time the spring 11 is compressed, and the latters expansion, occurring when reversing valve II is again shii'ted to relieve the pressure on plunger 86, is made eflective through pawl 84 to return the tool each time to its established radial position at the start of a boring operation on a new workpiece.

Also on each reversal of table 2 at the left hand end of its movement, the pressure fluid is directed through conduit 21 and branch conduit 21' against the right hand, end of gage-moving plunger 24, causing the gage 22 to enter the flnished workpiece 4 if the latter, by the passage therethrough oi the tool 3 has been enlarged to the desired size. In those instances that the gage 22 does enter the workpiece bore, indicating that the boring operation performed thereon has produced the desired size, there is no access 01' the pressure fluid to the conduit 92 and port 9| since the ports 20 and 29 are kept from communicating with each other by the plunger 24, the latter having been permitted by said gage entry to move to its extreme left hand position. In the regular and ordinary operation of the machine, this entry of the gage will be permitted by quite a number of consecutive workpieces, and so long as these conditions prevail there will be no change made in the established radial position of the tool 3, other than its temporary back-off, as above described during each withdrawal stroke of the table. 1

However, as a result of the gradual wearing down of the tool I, from a number of such boring operations, said tool may ultimately produce a bore which is undersize, that is, a bore not large enough to permit the entry of the gage 22. When this occurs, on the right hand or withdrawal movement 01' table 2, the usual movement of the gage 22 to the left is limited by contact between the gage and the end of the workpiece, thereby stopping the plunger 24 in mid-position and establishing, by means of groove 28, a fluid connection between the ports 20 and 29. Accordingly, later on in this same right hand withdrawal movement of the table, when the dog 4i engages and depresses the stem 40 of valve 31 (whether or not workpiece a has moved clear of tool 3) the fluid under pressure from pump is is admitted by reduced portion 45 of valve 31 to conduit 34, and this fluid, by reason of the stoppage of plunger 24 in mid-position, in the situation above described, is admitted by way of conduit 92 and port 9| against the plunger 84. The ensuing movement of plunger 84 to the right gives the rod 18 an additional right hand movement, over and above that produced as above described, by the plunger u.

Consequently, in the situation assumed (nonentry of gage 22 into a finished workpiece bore) there is a further .movement of rod 18 that, through pin H, turns plate 6i counterclockwise a little beyond the point where pawl 65 engages,

and is made inoperative by, the pin 88. Beyond that point, therefore, does not partake of the further slight counterclockwise motion of plate 6 I. Consequently, when the fluid pressure against plungers II and 84 is later relieved at the start oi a new boring operation, the spring 11, in causing the clockwise motion that restores the approximate conditions through pawl 64, move cap 52 clockwise a little in excess 01 the previous counterclockwise motion of said cap.

In other words when spring 'll becomes ell'ective for clockwise restoration of said parts, the point of tool 3, because of the eccentric mounting of cap 52, will be set slightly out from its previously established position. In this way the tool is repositioned automatically, in response to each non-entry oi gage 22 into any finished workpiece bore to compensate for the wear that has resulted in an undersize bore. Following each such repositioning of the tool 2, the machine operations continue on a succession of workpieces with a temporary back-of! of the tool on each reverse or withdrawal stroke of the table, as above described; it the successive operations-so wear down said tool as to cause production of another undersize bore another automatic repositioning of the tool occurs, to compensate for such wear.

I claim:

1. In a boring head, a housing, a spindle Journalled therein, a tool carried by and adjustable radially of the spindle, a rod axially movable in the spindle, means responsive to axial movement of the rod for retracting the cutting point of the tool radially or the spindle, and other means responsive to additional movement of the rod in the same direction for procuring adjustment of the operative position 01' the cutting point of the tool radially of the spindle in a direction opposite to said retracting movement.

2. In a boring machine, a housing, a spindle journalled therein, a tool carried by and adjustable radially of the spindle, a rod axially movable in the spindle, means responsive to axial movement of the rod for procuring an inward movement of the tool radially oi the spindle, means responsive to additional axial movement of the rod in the same direction for adjusting the position 0! the cutting point of the tool outwardly radially of the spindle, and separate fluid pressure actuated means for actuating the rod for each of the shifting and adjusting movements of the tool.

3. In a boring machine, a housing, a spindle joumalled therein, a tool carried by and adjustable radially of the spindle, a rod axially movable in the spindle, means responsive to axial movement of the rod for procuring an inward movement of the tool radially of the spindle, means responsive to additional axial movement of the rod for procuring adjustment of the operative position of the cutting point of the tool outwardly radially oi the spindle, and separate means for procuring each axial movement of the rod.

4. In a boring machine, a housing, a spindle journalled therein, a cap eccentrically mounted on the end'of the spindle, a boring tool carried by the cap, and means operable independently of the spindle rotation for shifting the cap angularly of the spindle in a direction to move the boring tool inwardly radially of the spindle.

5. In a boring machine, a housing, a spindle Journalled therein, a cap eccentrically mounted on the end of the spindle, a boring tool carried by the cap, means operable independently of the the cap 52 carrying tool I,

spindle rotation for shifting the cap angularly 'oi the spindle in a direction to move thefboring tool inwardly radially of the spindle, and} fluid pressureactuaior for said means.

6. In a boring 'machine, a housing, a spindle journalled therein, a cap eccentrically niounted on the end of the spindle, a boringtool carried by :the cap, a rod axially slidable in the sp nd e, a

plate turnable relative to the spindle injjrje sponse to axial movement of the rod, a pawlon said,

by the cap, a. rod axially slidable' in thespindle,

a plate turnable relative to the spindjle'ln response to axial movement of the rod, cooperating pawls on said plate and a ratchet on thecapcooperating therewith, said pawls procuringmoveable in the spindle, work calipering means, and

means under the control of said work calipering means and operative when a workpiece in the workholder is not finished to the desired dimenment of the cap with said plate, and means for rendering one of said pawls inoperative during a portion of the turning movement of theplate',

8. In a boring machine, a housing, afspindle journalled therein, a tool carried by and adjustable radially oi the spindle, a rod axially movable in the spindle, means responsive to axial movement of the rod for procuring an inward movement of the tool radially of the spindle, means responsive to additional axial movement of the rod in the same direction for adjusting the operative position of the cutting point of the tool outwardly radially of the spindle, and a fluid pressure actuated plunger for shifting said rod for the inward movement of the tool.

9. In a boring machine, a housing, a spindle journalled therein, a tool carried by and adjustable radially of the spindle, a rod axially movable in the spindle, means responsive to axial movement of the rod for procuring an inward movement of the tool radially of the spindle, means responsive to additional axialmovement of the rod in the same direction for adjusting the operative position of the cutting point of the tool outwardly radially of the spindle, a fluid pressure actuated plunger for said first axial movement'oi the rod, and an additional fluid pressure actuated plunger for procuring the additional axial movement of the rod.

10. In a machine of the class described, a workholder, a tool holder comprising a housing, a rotary spindle journalled therein and a tool carried by and movable radially oi the spindle, means for procuring a boring operation on a workpiece in the workholder and a subsequent relative withdrawal movement of the tool from the workpiece bore by relative axial movement of the workpiece and tool, means operative at the beginning of the withdrawal movement for shifting the tool radially inward oi the spindle, said means including an actuating rod axially movable in the spindle, and fluid pressure actuated means for shifting said rod.

11. In a machine of the class described, a

workholder, a tool holder comprising a housing, a 0

rotary spindle journalled therein and a tool carried by and movable radially of the spindle, means for procuring a boring operation on a workpiece in the workholder and a subsequent relative withdrawal movement of the tool from the workpiece bore by relative axial movement of the workpiece and tool, means operative at the beginning of the withdrawal movement for shifting the tool radially inward of the spindle, said means including an actuating rod axially mov- 'sion for adjusting the normal position of the tool relative to the spindle. 12. In a machine of th class described, a workholder, 9. tool'holder comprising a housing, a rotary spindle journalled therein and a tool carried by' and movable radially of the spindle,

means forprocuring a boring' operation on a workpiece in the workholder and a subsequent relative withdrawal movement of the tool from the workpiece bore by relative axial movement of the workpiece and tool, means operative at the beginning of the withdrawal movement for shifting the tool radially inward of the spindle, said means including an actuating rod axially movable in the spindle, work calipering means, and means under the control "of said work calipering means and operativev when a workpiece in the workholderisj not fln'i'shed to the desired dimensionior adjusting the normal position oi the tool relative to the spindle, said last'adjustment being procured by axial movement of the actuating rod.

13. In a machine of the class described, a workholder, a tool holder, said tool holder including a rotary spindle and a boring tool radially adjust able thereon, work calipering means in a position to test the dimension of a finished workpiece and operative upon separation of the tool from a workpiece in the workholder, fluid pressure actuated means for adjusting said tool relative tothe spindle, a valve associated with said work calipering means for directing fluid pressure to said adjusting means only when the work calipering means indicates that the workpiece is not the desired dimension, and other fluid pressure actuated means operative at the beginning of the separation of the tool from the workpiece for shifting the tool inwardly radially of the spindle.

14. In a machine of the class described, a workholder, a tool holder having a rotary spindle on which the tool is mounted, means operable to adjust the position of the tool relative to the axis ofrotation of the spindle, a gage brought into action by the completion of the tools operation on each workpiece in said workholder to test the dimension of the finished surface of said workpiece,-a valve associated with said gage, fluid pressure actuated means for operating said adlusting means-said valve directing fluid to said fluid actuating means in response to obstruction oi said gages passage along the tooled surface or the workpiece, and additional fluid pressure actuated means operative at the completion of the tools operation on each workpiece for shifting the position of the tool relative to the axis of rotation of the spindle in a direction opposite to the aforesaid tool movement by the adjusting means.

15. In a machine of the class described, a boring tool and a workholder. means for imparting rotation to one of said parts, means for traversing one part relatively to the other for a boring operation by said tool on each of a succession of working position,

position, and means responsive to non-entry of said use intoany bore on which said tool has operated for procuring said tools outward radial projection, by the start of the next boring operation, beyond said previously-established working position.

16. In a machine or the class described, a borl and a workholder, means for imparting rotation to one of said parts, means for traversing one part relatively to the other for a boring operation by said tool on each of a succession of workpieces disposed in said workholder, a gage alined with said workholder to test the bore size 01 each workpiece, means rendered operative by reversal of said traverse for radially retracting said tool from its previously established working position and for urging said gage toward the bore just operated upon by said tool, means responsive to the start of the next boring operation for restoring the retracted tool to its established workif said case on said reverse stroke has entered the bore Just operated upon by said tool, and means for procuring by said start of the next boring operation a slight additional outward projection of said tool beyond said previously-established working position, if said bore has not permitted the entry of said gage.

17. In a machine of the class described, a boring tool and a workholder, mean; for imparting rotation to one or said parts. means for traversing one part relative to the other for a boring operation by said tool on each of a succession oi workpieces disposed in said workholder, a sage alined with said workholder to test the bore size oi each workpiece, fluid pressure means rendered operative by reversal of said traverse for radially retracting said tool from its previously-established working position and for urging said sale toward the bore just operated upon by said tool, spring means responsive to the start of the next boring operation for restoring the retracted tool to its established working position, and means responsive to non-entry oi said gage into any bore on which said tool has operated for procuring said tools outward radial projection, by the start,

oi? the next boring operation, beyond said previously-established working position.

HAROLD L. BLOOD. 

